Cathodic protection of internal combustion engines



y 23, 1963 D. A. YOUNG ETAL 3,098,473

CA'TI-IODIC PROTECTION OF INTERNAL COMBUSTION ENGINES Filed Jan. 25,1962 FIGURE I EFFECT OF CATHODIC PROTECTION OF ENGINE PARTS IN I6 HOURENGINE RUST TEST PROTECTED\ 9o I I0 I I I I ABSOLUTE HUMIDITY 0F ENGINEINTAKE AIR GRAINS OF MOISTURE/LB. 0F DRY AIR FIGURE 2 DALE A-YOUNGINVENTORS GEORG J. FARRIS BYJMQ flat PATENT ATTORNEY 1 engine.

3,fi98,473 Patented July 23, 1963 3,098,473 CATHGDIC PROTECTION (ll?INTERNAL CGUS'IH'UN ENGJZNES Dale A. Young, Roselle Park, NJ and GeorgeJ. Farris,

Chicago, EL, assignors to Esso Research and Engineering Company, acorporation of Delaware Filed Jan. 25, 1962, Ser. No. 168,763 7 Ciairns.(Ci. l23-%) This invention relates to a method and apparatus forinhibiting corrosion of internal combustion engines. In particular, theinvention pertains to a sacrificial anode technique for protectingautomotive engines against corrosion. Even more particularly, theinvention pertains to the prevention of valve train assembly, e.g.hydraulic valve lifter rusting by the use of a sacrificial anode.

A full understanding of the invention may be had by referring to thefollowing description and claims taken in conjunction with theaccompanying drawing in which FIG. 1 shows a view of a rocker armassembly with a Zinc strip held in place with one of the hold-down boltsof said assembly, and FIG. 2 shows a graph of rust vs. humidity in anengine rust test.

' For several years now hydraulic type valve lifters have been used inincreasing members in automotive engines. Any rusting tendencies withinthe engine become significant since these tendencies affect theoperation of the hydraulic valve lifters. Hydraulic valve liftersgenerally comprise a cylindrical body, within which is an axiallyslidable plunger. The most detrimental corrosion or rusting occurs atthe parts of contact between the plunger and the interior of the lifterbody. Corroded hydraulic valve lifters tend to stick and create noise aswell as to promote the possibility of serious engine damage because oftheir improper operation.

In order to prevent this corrosion of hydraulic valve lifters,lubricating oil manufacturers have incorporated rust preventivechemicals in their oil formulations. However, the requirements of amodern, internal combustion engine also dictate that an elfectivemotoroil formula- .tion must also contain a detergent-inhibitor in orderto suspend any sludge formed. Unfortunately, chemical rust inhibitorsand detergent-inhibitors have been found to be somewhat antagonistic toeach other. Thus, inclusion of a rust preventive compound and adetergent inhibitor compound detracts from the potential efiectivenessof either one if used alone It has now been discovered and forms thesubstance of this invention, that the problem can be alleviated by theuse of a sacrificial anode located properly within the In the past,sacrificial anodes in the form of magnesium nickel alloy drain plugswere used, but with little success. The reason for this is believed tobe that the sludge formed within the engine settles to the bottom of thecrankcase thus forming a film on the surface of the drain plug. Thisfilm provided sufiicient resistance to the galvanic circuit necessary ina sacrificial anode apparatus to effectively stifle galvanic action.Furthermore, it is believed that the drain plug is too far removed fromthe parts to be protected, i.e. the hydraulic valve lifters, to form asuitable galvanic couple with these parts.

The most informed current view of the major cause of corrosion within aninternal combustion engine is that it is due to galvanic corrosion. Bygalvanic corrosion is meant the accelerated attack on metals whichresults from the flow of current between dissimilar metals in electricalcontact in a liquid capable of conducting current. Conditions necessaryfor galvanic corrosion are that there be a combination of dissimilarmetals having a potential dilierence when they are in a corrosiveenvironment, an electrical connection between the dissimilar metals sothat electrons can flow from one metal to another and an ionized liquidcapable of conducting current between the dissimilar metals. Since theWaste exhaust products such as water and blowby gases which contaminatethe lubricating system of an internal combustion engine are stronglyionic, it will be recognized that all the above-named conditions arepresent in an internal combustion engine. The term dissimilar metals isused in a very broad sense; thus, two types of steel might bedissimilar, i.e. a carbonized steel and a chromium steel, or cast ironor wrought iron can be sufficiently dissimilar to set up a galvaniccouple. In a galvanic couple the flow of electrons is from the anode tothe cathode. Thus, it is the anode part of the galvanic couple whichtends to corrode. It is also known that the greater the surface area ofthe cathode relative to an anode, the more severe the corrosive elfecton the anode.

Therefore, in order to protect the metal in a particular environment, iti known to provide an anodic material in that environment which ishigher in a galvanic series than the material to be protected. In thiscase since steel or iron can be considered the material to be protectedit should be the cathode and a sacrificial anode must be higher in thegalvanic series. Suitable materials higher in the galvanic series thansteel or iron include cadmium, zinc, magnesium, in that order. Althoughthese are the preferred metals, it will be understood that other metalsand metal alloys can be used as long as they are higher in the galvanicseries than the metal to be protected in the specific environment underconsideration. The metal to be protected then becomes a cathode and themetal higher in the galvanic series then becomes an anode and iscommonly referred to as a sacrificial anode.

Another important factor in the use of a sacrificial anode is thelocation of such anode. Thus, preferably, the anode should be located asclose as possible to the particular cathodic material it is desired toprotect. For instance, when it is desired to protect against corrosionof hydraulic valve lifters, especially the tappet portion, thesacrificial anode should be located as close to such valve lifter aspossible. The importance of location then is twofold, one aspect beingto increase the elfectiveness of the sacrificial anode and the other toeliminate the possibility of films, such as sludge, forming on the metalsurfaces which could increase the resistance of the galvanic circuit toan extent sufficient to nullify the galvanic action. Since the hydraulicvalve lifter assembly is located close to the top of an internalcombustion engine both sludges and other film forming substances areconstantly washed off the hydraulic valve lifter assembly surfaces.Also, since these substances are generally heavier with respect to themain body of oil they tend to find their way to the bottom of theautomobile engine block.

In utilizing the sacrificial anode of this invention, two generaltechniques can be employed both of which are equally satisfactory. Oneof these is to attach a strip of the sacrificial anode metal to aconvenient location near the hydraulic valve lifter assembly. In someinstances this can present difficulties since the tolerances of valvelifter assemblies are quite close. A convenient place and one that wasused in a specific embodiment of this invention is one of the holddownbolts for the rocker arm assembly. However, the sacrificial anode metalcan be attached by any convenient technique such as a rivet, bolt,adhesive such as an epoxy resin and the like. The only criticallimitation is that a complete metallic circuit for the electron flowmust be maintained.

The other technique is to deposit a film of the sacrificial anode metalon, or near, the portion of the engine that is most susceptible tocorrosion and most in need of protection. Thus, various portions of thevalve train assembly can be galvanized with a metal such as zinc, i.e.zinc plated push rods. Such galvanization or other deposition techniquessuch as vapor deposition will effectively avoid any problems caused bytolerance limitations in the design of the hydraulic valve train.

' With reference to the drawing, rocker arm assembly 1 is shown rigidlyattached to cylinder head 2 by means of holddown bolts 3 and 4. Theupper portion of push rod 5 engages rocker arm 6 which is part of rockerarm assembly 1. Zinc strip 7 is rigidly attached to rocker arm assembly1 by holddown bolt 3.

It will be understood that although particular mention has been made tothe hydraulic valve lifters, it is possible to satisfactorily protectthe entire valve train as sembly. The valve train assembly includes thehydraulic valve lifter, push rod, rocker arm assembly, valve, valvespring and cam shaft.

The invention will be more fully understood by reference to thefollowing example.

Example 1 In order to demonstrate the outstanding rust inhibitionresults obtained by using the sacrificial anode technique of theinvention a series of tests was carried out in an ER4-99 rust test.

The ER4-99 rust test is designed to provide a method for ratingautomotive crankcase lubricants for their rust preventive qualities.This technique involves the continuous operation of a CLR engine atconstant speed and load for 16 hours under conditions conducive to theformation of engine rust.

The test uses a single cylinder CLR Oil Test Engine equipped withstandard carburetion, external water and oil cooling, and a screwmechanism to regulate blowby. The CLR engine is an abbreviation for theCooperative Lubricant Research engine which is manufactured by theLaboratory Equipment Corp. (LABECO) of Indianapolis, Ind. The testprocedure and conditions are fully described in a paper entitled,Evaluation of Rusting Characteristics of Motor Oils by D. A. Young andG. J. Farris presented at the 1961 SAE National Fuels and LubricantsMeeting at Houston, Texas on or about November 9, 1961.

In brief, each run lasts for a duration of 16 hours at any selectedintake air humidity measured in terms of grains of moisture per pound ofdry air. In this series of runs a commercial lubricating oil was usedcontaining conventional detergent inhibitors, rust inhibitors, V. I.improvers and pour point depressants. In the engine which wasunprotected by a sacrificial anode seven 16- hour runs were made. Onerun was made at an engine intake humidity of approximately 108 grains ofmoisture per pound of air. Two runs were made at an approximate humidityof about 111 grains of moisture per pound of air and four runs were madeat a humidity of about 128 grains of moisture per pound of air.

A zinc strip approximately one inch wide by two and one-half inches longwith a thickness of about 20 gauge was afiixed to the rocker armassembly of the CLR engine by means of a holddown bolt as illustrated inFIG. 1. Two 16-hr. runs were made in the engine protected with the zincstrip. One of such runs was made at a humidity of approximately 129grains of moisture per pound of air and the other such run was made at ahumidity of about 141 air grains of moisture per pound of dry air. Foreach run the push rods were polished anew, new hydraulic valve lifterswere installed, and fresh oil was used. The push rods and hydraulicvalve lifters were rated for rust at the conclusion of each 16- hourrun. The rating was made on the basis of the 6.1M. scale wherein 0equals heavy rust and 10 equals no rust at all. The results obtained aresummarized in the FIG. 2 graph.

it can be seen from the graph that ordinarily as the amount of moistureincreases the amount of rust within the engine also increases. Forequivalent amounts of moisture in the engine intake, the series of runswhere the engine was protected by the sacrificial anode, showsconsiderably less rust than comparable runs made with no anodicprotection.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that numerous changesin the details of operation and construction and the combination andarrange ment of parts can be resorted to without departing from thespirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. A method of protecting an oil-containing lubricating system of ametallic internal combustion engine against corrosion which comprisespositioning a sacrificial anode within the oil of said lubricatingsystem at a relatively sludge-free location sufiiciently close to themetal part of said system desired to be protected to form a galvaniccouple therewith, said sacrificial anode being composed of metal higherin the galvanic series than said metal part desired to be protected, andsaid relatively sludgefree location being chosen such that sludgesnormally formed within said lubricating system cannot depositsufiiciently on said sacrificial anode to prevent the fiow of electronsand ions between said anode and said metal part desired to be protected.

2. A method according to claim 1, wherein said metal part desired to beprotected is the hydraulic valve train assembly and wherein saidsacrificial anode is located proximate to said hydraulic valve trainassembly.

3. A method according to claim 1 wherein said protective metal is zinc.

4. A method according to claim 2 wherein said protective metal is zinc.

5. In combination with a metallic oil-containing lubricating system ofan internal combustion engine, a cathodically protected hydraulic valvetrain assembly comprising a valve train assembly having a rocker armassembly, and a sacrificial anode attached to said rocker arm assembly,said sacrificial anode being composed of metal higher in the galvanicseries than any component metal in said hydraulic valve train assembly.

6. A method of reducing hydraulic valve lifter sticking in thelubricating system of a metallic internal combustion engine whichcomprises positioning a sacrificial anode composed of metal higher inthe galvanic series than the metal of said hydraulic valve lifterproximate to said hydraulic valve lifter to thereby form a galvaniccouple therewith and to reduce corrosion of the metallic parts of saidvalve lifter by cathodic protection.

7. A method according to claim 5, wherein said metal of said hydraulicvalve lifter is iron.

References Cited in the file of this patent UNITED STATES PATENTS

5. IN COMBINATION WITH A METALLIC OIL-CONTAINING LUBRICATING SYSTEM OFAN INTERNAL COMBUSTION ENGINE, A CATHODICALLY PROTECTED HYDRAULIC VALVETRAIN ASSEMBLY COMPRISING A VALVE TRAIN ASSEMBLY HAVING A ROCKER ARMASSEBLY, AND A SCRIFICIAL ANODE ATTACHED TO SAID ROCKER ARM ASSEMBLY,SAID SACRIFICIAL ANODE BEING COMPOSED OF